The present invention relates to pipe conduits in general, and more particularly to a method of salvaging or restoring to use a pipe conduit which has suffered damage.
There are already known various methods of salvaging a pipe conduit which is buried under ground, especially of a sewage or waste water channel. Generally speaking, such methods include the use of a lining hose having a diameter which is slightly smaller than the inner diameter of the pipe conduit to be salvaged. This lining hose frequently includes an impermeable layer and an adjacent resin-absorbing layer. This resin-absorbing layer is soaked or permeated with a resin prior to the introduction of the thus treated lining hose into the pipe conduit. The lining hose is introduced into the pipe conduit in its collapsed state by means of a rope or cable and a winch. After being properly positioned in the pipe conduit, the liming hose is pressed against the inner surface of the pipe conduit by a pressurized medium.
One method of this kind is known from the German patent DE-PS No. 22 40 153. This method employs a lining hose which is provided with the impermeable layer at its exterior. The alleged purpose of this impermeable outer layer is to avoid the need for preceding cleaning of the pipe conduit. However, it was established by experience that a thorough cleaning is necessary, inasmuch as deposits are always present in an old pipe conduit, and these deposits often occupy a considerable part of the flow-through cross-sectional area of the pipe conduit.
Since a connection of the lining with the inner surface of the pipe conduit cannot take place through the impermeable outer layer, leaky locations, such as cracks or fissures in the pipe conduit or damaged pipe connections, are not sealed, so that ground water which penetrates from the ground into the pipe conduit through such leaky locations collects in the annular space present between the inner surface of the pipe conduit and the outer surface of the lining. Also, the securing of the lining in the pipe conduit against displacement in the axial direction of the pipe conduit cannot be achieved in this construction. This lining is provided with a resin-impermeable layer even at its inner surface.
There is further known, from the German patent DE-PS No. 23 62 784, a method in accordance with which the lining hose which is introduced into the pipe conduit to be salvaged is provided with the resin-impermeable layer at its inner region, and with the resin-soaked layer at its outer region. This lining hose is introduced into the interior of the pipe conduit by turning over one end region thereof and by causing the turned-over region to gradually advance into the interior of the pipe conduit. During the performance of this last-mentioned step, the resin-soaked layer, which is originally located at the interior, is gradually transferred to the exterior of the lining hose. Relatively high forces are needed for the gradual turning-over of the lining hose, owing to the fulling work to be performed at the turned-over region. Inasmuch as the lining hose is being turned over at the turning-over region with a relatively small radius, it is not possible to use a glass fiber reinforced lining hose.
Formation of folds or creases cannot be prevented when using these two known methods during the introduction of the lining hose into arcuate portions of the pipe conduit or into pipe conduit regions including positional shifting between axially successive pipe conduit sections. Yet, such folds or creases adversely affect the flow-through cross-sectional area, promote the formation of deposits, and their shapes are stabilized by the hardened resin. Such folds or creases must then be removed by a milling apparatus which moves through the lined pipe conduit. Inasmuch as the lining is damaged by this milling operation, an additional hose is subsequently introduced into the interior of the lined pipe conduit and is adhesively connected with the lining.